CAMBRIDGE, Mass. — Scholar Rock said the U.S. Food and Drug Administration has granted Fast Track and Orphan Drug designations to apitegromab for the treatment of facioscapulohumeral muscular dystrophy, or FSHD, as dosing begins in the Phase 2 FORGE clinical trial.
Apitegromab is an investigational fully human monoclonal antibody designed to inhibit activation of myostatin, a protein involved in regulating skeletal muscle growth.
FSHD is a rare hereditary neuromuscular disease characterized by progressive muscle atrophy, weakness and functional decline. There are currently no approved therapies for the disease.
“We are very pleased to receive both Fast Track and Orphan Drug designations for our apitegromab FSHD program, which underscores the urgency of advancing new treatment options for the FSHD community,” said David L. Hallal, Chairman and CEO of Scholar Rock. “With participant dosing now underway in our Phase 2 FORGE study, we are one step closer to realizing the broader potential of our world-leading myostatin platform and bringing a potentially transformative muscle-targeted therapy to people living with FSHD worldwide.”
FORGE is a randomized, double-blind, placebo-controlled Phase 2 trial evaluating the efficacy, safety, pharmacokinetics and pharmacodynamics of apitegromab as a monotherapy in adults with genetically confirmed FSHD.
The study is expected to enroll approximately 60 participants who will be randomized to receive either apitegromab at 10 mg/kg or placebo intravenously every four weeks for 52 weeks.
The primary endpoint is the percentage change from baseline in total lean muscle volume, measured by MRI at Week 52. Secondary measures include changes in lean muscle volume at Week 24, muscle fat fraction, and safety and tolerability.
“Our preclinical data from the FlexDux4 model and prior literature suggest that, in people living with FSHD, anabolic stimuli can result in muscle hypertrophy and improved motor function,” said Akshay Vaishnaw, M.D., Ph.D., President of Research and Development at Scholar Rock. “We believe FORGE, which assesses changes in lean muscle volume as well as a range of exploratory functional endpoints, will enable robust evaluation of apitegromab and inform on the drug’s potential to drive meaningful functional outcomes.”
Scholar Rock said preclinical studies using an FSHD mouse model found that a murine form of apitegromab increased muscle mass, strength and endurance.
Apitegromab is also being developed for spinal muscular atrophy. Scholar Rock said the therapy previously demonstrated statistically significant and clinically meaningful improvement in motor function in a Phase 3 study of patients with SMA receiving an SMN-targeted therapy.
The FDA’s Fast Track program is intended to accelerate the development and review of therapies for serious conditions with significant unmet medical needs. Apitegromab has not been approved for any indication by the FDA or other regulatory authorities.
